Low, moderate, or high protein yogurt snacks on appetite control and subsequent eating in healthy women

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Low, moderate, or high protein yogurt snacks on appetite control and
subsequent eating in healthy women
Steve M. Douglas
a
, Laura C. Ortinau
a
, Heather A. Hoertel
a
, Heather J. Leidy
a,b,
⇑
a
University of Missouri, Dept. of Nutrition, 204 Gwynn Hall, Columbia, MO 65201, United States
b
Dept. of Nutrition & Exercise Physiology, School of Medicine, 204 Gwynn Hall, University of Missouri, Columbia, MO 65211, United States
article info
Article history:
Received 28 May 2012
Received in revised form 29 August 2012
Accepted 16 September 2012
Available online 25 September 2012
Keywords:
Snacking
High protein
Yogurt
Appetite
Satiety
abstract
This study assessed whether afternoon snacks, varying in protein content, influence appetite-control and
eating initiation. Fifteen healthy women (age: 26 ± 2 y) randomly consumed 160 kcal afternoon yogurt
snacks containing Low (LP), Moderate (MP), or High (HP) protein (5,14, 24 g protein, respectively) or
had no snack (NS) for 3 days. On day 4, the volunteers came to our facility to consume a standardized
lunch. The respective snack pattern was completed 3 h post-lunch. Perceived sensations were measured
every 30 min until dinner was voluntarily requested. An ad libitum dinner was then provided. Snacking,
regardless of protein content, led to reduced hunger and increased fullness, which were sustained up to
120 min post-snack vs. NS (all, p< 0.05). Between snacks, hunger was lower and fullness was higher
throughout post-snack following HP vs. LP (p< 0.05). Snacking delayed the onset of eating vs. NS (all,
p< 0.05). Specifically, dinner was requested at 124 ± 7 min following NS, 152 ± 7 min with LP,
158 ± 7 min following MP, and 178 ± 7 min post-snack for HP. Between snacks, HP led to the latest
request time vs. LP (p< 0.001) and MP (p< 0.05). Although the energy content consumed at dinner
was lower following the yogurt snacks vs. NS, the 160 kcal snacks were not fully compensated for at this
meal. In conclusion, an afternoon snack of Greek yogurt, containing 24 g protein, led to reduced hunger,
increased fullness, and delayed subsequent eating compared to lower protein snacks in healthy women.
Ó2012 Elsevier Ltd. All rights reserved.
Introduction
Modest increases in dietary protein have become part of suc-
cessful, dietary strategies for weight loss, as well as, the prevention
of weight re-gain following weight loss (Leidy & Carnell et al.,
2007; Westerterp-Plantenga et al., 2009). One key factor in the
effectiveness of higher protein diets, compared to high fat and/or
high carbohydrate versions, is the observed improvements in
appetite control and satiety (Leidy & Carnell et al., 2007; Wester-
terp-Plantenga et al., 2009). Most of the additional protein in these
diets is incorporated into meals containing anywhere from 28 g
protein/meal to well over 100 g protein/meal (Leidy & Carnell
et al., 2007; Westerterp-Plantenga et al., 2009). Although these
meals elicit significant reductions in appetite and increases in
satiety, it is unclear as to whether smaller quantities of protein,
consumed as afternoon snacks, elicit similar benefits.
Some of the more commonly consumed higher-protein snacks
in the US include dairy products such as milk, cheese, and yogurt
which usually contain between 8 and 14 g of protein/serving (Pier-
nas & Popkin, 2010). In a recent article by Dougkas et al. (Dougkas
et al., 2012), isocaloric (i.e., 200 kcal) morning, dairy snacks con-
taining an average of 12 g of protein led to reduced appetite and
lunch intake compared to no morning snack. Furthermore, greater
reductions in appetite were observed with the yogurt snack com-
pared to the cheese and milk snacks (Dougkas et al., 2012). Since
many have speculated that the majority of snacking in the United
States occurs in the afternoon and evening, rather than the morn-
ing (Stachura, 2010), we recently completed a study that extends
these findings to examine the effects of consuming afternoon yo-
gurt snacks containing normal (5 g protein) vs. increased protein
(14 g protein) on appetite control and satiety (Ortinau, Culp,
et al., 2012). We also incorporated a more accurate assessment of
satiety by allowing the participants to voluntarily request dinner
based on motivational state/drive to initiate eating (Marmonier,
Chapelot, et al., 2000; Ortinau et al., 2012). Regardless of protein
content, both yogurt snacks equivalently reduced hunger, in-
creased fullness, and delayed the onset of eating compared to no
snack (Ortinau et al., 2012). However, no differences were found
between yogurts, suggesting that additional protein (P14 g) is re-
quired to elicit protein-related benefits on appetite control and
satiety (Ortinau et al., 2012).
In 2008, Greek yogurt was introduced into the United States
with sales increasing exponentially over the past several years
(The Nielsen Company, 2010). The increased frequency of
0195-6663/$ - see front matter Ó2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.appet.2012.09.012
⇑
Corresponding author.
E-mail address: leidyh@missouri.edu (H.J. Leidy).
Appetite 60 (2013) 117–122
Contents lists available at SciVerse ScienceDirect
Appetite
journal homepage: www.elsevier.com/locate/appet

consumption, along with the increased protein content of Greek
yogurt (20–24 g/serving) (USDA, 2011), which is almost 5 times
that of regular yogurt, make this a potentially ideal snack option.
The purpose of this study was to assess whether the consump-
tion of afternoon yogurt snacks, varying in protein content from 5
to 24 g protein, influence afternoon appetite and satiety responses
and delay the onset of eating. As discussed above, eating initiation
(i.e., the onset of eating) has been previously validated and utilized
in other snack studies as an excellent, novel indicator of motiva-
tional drive to eat and ‘‘satiety power’’ (Himaya, Fantino, et al.,
1997; Marmonier et al., 2000).
Methods
Participants
Healthy, pre-menopausal women chose to participate in this
study by responding to flyers posted on the University of Missouri
(MU), Columbia campus or through the MU-listserv. Eligibility in-
cluded the following: (1) age 18–50 y; (2) normal to overweight
(BMI between 18 and 27 kg/m
2
); (3) no metabolic diseases/condi-
tions; (4) not been clinically diagnosed with an eating disorder; (5)
not currently on a weight loss or other special diet (in the past
6 months); (6) not a smoker (in the past year); (7) habitually eat
(i.e., at least 5 times/wk) breakfast between 7:00 and 9:00 am,
lunch between 11:00 am and 1:00 pm, an afternoon snack between
2:00 and 4:00 pm, and dinner; (8) no food allergies or intolerances
to dairy products; (9) and rated the overall liking of the study
snack foods higher than ‘‘Neither Like nor Dislike’’ on the screening
palatability questionnaire.
Twenty-two participants began the study. Of these, 15 (age:
26 ± 2 y; BMI: 22.3 ± 0.5 kg/m
2
) completed all study procedures.
Of those that did not complete the study, seven had unusable per-
ceived appetite and satiety responses due to computer program-
ming errors. All participants were informed of the study
objectives, procedures, and risk. Written informed consent was ob-
tained from all participants. The study was approved by the MU
Human Subjects’ Institutional Review Board. The participants re-
ceived $300 for completing all study procedures.
Experimental design/study procedures
The study incorporated a randomized crossover design compar-
ing the consumption of 160 kcal afternoon yogurt snacks contain-
ing Low Protein (LP, 5 g protein), Moderate Protein (MP, 14 g
protein), and High Protein (HP, 24 g protein) vs. no snacking (NS).
Prior to the start of the study, the participants were asked to
document their habitual breakfast, lunch, and afternoon snack
times. The snack patterns and associated testing days were
scheduled so that each participant consumed the afternoon snack
(or refrained from snacking) 3 h after lunch; however, the time
of day when this occurred was based on the participant’s previous,
habitual snack time. Once this was determined, the participants
were acclimated to each snack pattern for 3 consecutive days. Dur-
ing the acclimation days, the participants simply refrained from
eating a snack (i.e., NS) or consumed 1 of the 3 study yogurt snacks
provided. Four ounces of water was also consumed at this time.
On day 4 of each pattern, the participants consumed a standard-
ized breakfast, at home, and reported to the MU Brain Imaging
Center 1 h prior to lunch to begin the 8 h testing day (Fig. 1). Each
volunteer was placed in a comfortable room, absent of time cues.
The room contained a recliner, workstation, and laptop computer
for the participants to use, at leisure, throughout the day. The test-
ing day began with the consumption of the standardized lunch
meal. The respective snack pattern was completed 3 h after lunch.
This included the 160 kcal snack (or no snack) and 8 oz of water.
Perceived appetite and satiety questionnaires were completed
every 30 min throughout the remainder of the day. When the par-
ticipant requested to eat again, an ad libitum dinner was provided.
Regardless of time of dinner request, the volunteers were required
to remain in the facility until the full 8 h testing day was
completed.
Snacks
The dietary characteristics of the snacks are shown in Table 1.
All yogurt snacks were commonly consumed, commercially avail-
able products, similar in energy content and varying in protein
quantity. Specifically, the LP yogurt was 14% protein, 76% CHO,
and 10% fat; the MP yogurt was 36% protein, 64% CHO, and 0%
fat; and, the HP yogurt contained 60% protein, 40% CHO, and 0%
fat. To control for energy content and to examine commercial prod-
ucts, energy density, dietary fat, sugar, and fiber were not held
constant.
The sensory properties (i.e., aroma, flavor, texture, and overall
liking (palatability)) of each snack were assessed using a comput-
erized 100 mm VAS scale questionnaire during screening and after
the first and last bite of each snack during the acclimation and test-
ing days (Table 1). The questions are worded as ‘‘how strong is the’’
with anchors of ‘‘not all’’ to ‘‘extremely.’’ The Adaptive Visual Ana-
log Scale Software (Neurobehavioral Research Laboratory and
Clinic; San Antonio, TX) was used for these assessments.
Meals
During the morning of each testing day, a 300 kcal breakfast
meal was provided. The breakfast consisted of a breakfast quesa-
dilla and fruit. The macronutrient composition of the breakfast
Fig. 1. Diagram illustrating the 8 h testing day procedures.
118 S.M. Douglas et al. / Appetite 60 (2013) 117–122

was 15% protein, 60% CHO, and 25% fat. The participants consumed
this at home within 1 h after waking (between 7:00 and 9:00 am).
The participants were instructed to return all wrappers associated
with the pack-out breakfast foods as well as any potential remains.
In addition, the participants also documented that each component
of the breakfast meal was consumed.
During each of the testing days, a 500 kcal lunch meal was pro-
vided. The lunch consisted of a sandwich, chips, and applesauce
and was consumed within 30 min. The macronutrient composition
of the lunch was 15% protein, 55% CHO, and 30% fat; 8 oz of water
was also provided.
The ad libitum dinner consisted of chicken parmesan pizza
pocket pieces. The participants were instructed to eat as much as
they desired until feeling ‘comfortably full’ within 30 min. Addi-
tional pizza pocket pieces were given to the participants as needed.
All contents were weighed before the meal and the remaining con-
tents were weighed after the meal to determine the amount con-
sumed. Total dinner energy intake and macronutrient
composition were then determined.
Appetite and satiety questionnaires
Computerized questionnaires, assessing perceived sensations of
hunger, fullness, desire to eat, and prospective food consumption,
were completed throughout the testing days. The questionnaires
contain visual analog scales incorporating a 100 mm horizontal
line rating scale for each response. The questions are worded as
‘‘how strong is your feeling of’’ with anchors of ‘‘not all’’ to ‘‘extre-
mely.’’ The Adaptive Visual Analog Scale Software (Neurobehavior-
al Research Laboratory and Clinic; San Antonio, TX) was used for
these assessments.
Time to voluntary dinner request
In addition to the perceived appetite and satiety questionnaires
completed every 30 min, the participants were also asked whether
they would like to request dinner. When the response was ‘‘Yes, I
want to eat dinner right now’’, the time from snack consumption
was recorded. The participants were permitted to request dinner
in between the 30 min intervals if desired.
Data and statistical analysis
A power analysis was performed prior to the start of the study
to identify appropriate sample size. The time to dinner request
from Marmonier et al. (Marmonier et al., 2000) was used for this
analysis. The 60 min delay in dinner request between the high pro-
tein snack vs. no snack led to an effect size of 1.03, indicating that a
sample size of n= 15 would provide >80% power to detect a differ-
ence between snacks.
Summary statistics (sample means, and sample standard devia-
tions) were computed for all data. Total area under the curve (AUC)
was calculated from the postprandial time points for the perceived
sensations. A repeated measures ANOVA was applied to compare
the main effects of snacking on the following outcomes: afternoon
appetite and satiety; time to dinner request; and subsequent food
intake (at dinner). When main effects were detected, post-hoc pair
wise comparisons were performed using Least Significant Differ-
ences to identify differences between snacks.
Since many of the snack components were, by design, not
matched, there were numerous dietary and sensory factors that
might have contributed to the overall treatment effects. To identify
covariates, Pearson correlational analyses were first performed on
perceived snack aroma, flavor, texture, appearance, and palatabil-
ity responses and our primary outcome, that being time to dinner
request. Flavor (r: 0.347, p< 0.05) and palatability (r: 0.345,
p< 0.05) were found to be significantly associated with time to
dinner request and were thus included as potential covariates
using a mixed factor ANOVA. Because neither factor was found to
act as a covariate with snack pattern, the data is reported as unad-
justed means.
Pearson correlational analyses were also performed to identify
associations between protein content of the afternoon snacks and
study outcomes.
Analyses were conducted using the Statistical Package for the
Social Sciences (SPSS; version 19.0; Chicago, IL, USA). p< 0.05
was considered statistically significant.
Results
Perceived appetite and satiety
Figure 2 illustrates the post-snack perceived hunger responses
until dinner was voluntarily requested. Regardless of protein con-
tent, all yogurt snacks led to immediate reductions in hunger
which were sustained up to 120 min post-snack vs. NS (all,
p< 0.05). Between yogurts, HP led to lower post-snack hunger at
30, 90, and 150 min vs. LP (all, p< 0.05) and tended to be lower
at 150 min vs. MP (p= 0.08). Regarding the 120 min AUC assess-
ments, all yogurt snacks led to lower 120 min hunger AUC vs. NS
Table 1
Snack characteristics.
No snacking (NS) Low protein yogurt (LP) Moderate protein yogurt (MP) Higher protein yogurt (HP)
Dietary components
Energy content (kcal) – 160 160 160
Energy density (kcal/g) – 0.94 ± 0 0.94 ± 0 0.66 ± 0
Viscosity (Pa s) – 10.9 ± 0 38.4 ± 0 18.6 ± 0
Mass (g) – 170 ± 0 170 ± 0 255 ± 0
Volume (ml) – 170 ± 0 165 ± 0 250 ± 0
Total protein (g) – 5 14 24 .0
Total carbohydrates (g) – 30 .0 25 17
Sugar (g) 26 20 14
Fiber (g) 0 0 2.2
Total fat (g) – 1.5 0 0
Sensory components
A,B
Aroma – 75 ± 4 66 ± 4 74 ± 4
Flavor – 79 ± 3
a,b
70 ± 4
b
81 ± 3
a
Texture – 68 ± 6 70 ± 4 67 ± 6
Appearance 74 ± 4 68 ± 6 75 ± 5
Palatability (liking) – 78 ± 5 73 ± 3 79 ± 3
A
Data collected during the ‘last bite’ of the afternoon snack.
B
Difference letters denote significance.
S.M. Douglas et al. / Appetite 60 (2013) 117–122 119

(all, p< 0.05). HP led to lower 120 min hunger AUC vs. LP (p< 0.05),
but not MP. No other differences were detected.
Figure 3 illustrates the post-snack perceived fullness responses
until dinner was voluntarily requested. Regardless of protein con-
tent, all yogurt snacks led to immediate increases in fullness which
were sustained up to 120 min post-snack vs. NS (all, p< 0.05). Be-
tween yogurts, HP led to greater post-snack fullness at 60, 90, and
150 min vs. LP (all, p< 0.05) and at 150 min vs. MP (p< 0.05). MP
led to greater fullness at 60 min vs. LP (p< 0.05) Regarding the
120 min AUC assessments, all yogurt snacks led to greater
120 min fullness AUC vs. NS (all, p< 0.05). HP led to greater
120 min fullness AUC vs. LP (p< 0.05), but not MP. No other differ-
ences were detected.
Eating initiation
Eating initiation, as determined by time to dinner request, is
shown in Fig. 4. No snacking led to the earliest dinner request, at
approximately 2 h post-snack; LP and MP yogurts led to a dinner
request 2½ h post-snack; and, HP led to the latest request 3 h
post-snack. Statistically, all yogurt snacks delayed the onset of
eating vs. NS (all, p< 0.05). Between snacks, HP led to the latest on-
set of eating vs. LP and MP (both, p< 0.05). No other differences
were detected.
Ad libitum dinner
During the ad libitum dinner, the participants consumed
807 ± 51 kcal following NS, 737 ± 48 kcal with MP, 730 ± 36 kcal
following HP, and 705 ± 43 kcal with LP. All yogurt snacks led to
fewer kcal consumed at dinner vs. NS albeit only significant be-
tween LP vs. NS. Although the energy content at dinner was lower
following the yogurt snacks vs. NS, the 160 kcal snack was not fully
compensated for at this meal. Specifically, the LP snack led to a sur-
plus of +60 kcal, the MP snack of +90 kcal, and the HP snack of
+83 kcal. No differences were found between yogurt snacks.
Snack protein content and study outcomes
The relationship between the protein content of the yogurt
snacks and study outcomes were identified through Pearson Corre-
lation analyses. Protein content of the yogurt snacks was inversely
Fig. 2. Perceived hunger assessed throughout the post-snack period with 120 min area under the curve (AUC) shown to the right of the line graphs.

No snack (NS) vs. All
snack, p< 0.05;

high protein (HP) vs. low protein (LP), p< 0.05;
à
HP vs. moderate protein (MP), p= 0.08.
Fig. 3. Perceived fullness assessed throughout the post-snack period with 120 min area under the curve (AUC) shown to the right of the line graphs.

No snack (NS) vs. All
snack, p< 0.05;

high protein (HP) vs. Low protein (LP), p< 0.05;
à
HP vs. moderate protein (MP), p< 0.05;
§
MP vs. LP, p< 0.05.
120 S.M. Douglas et al. / Appetite 60 (2013) 117–122

associated with post-snack hunger AUC (r:0.457, p< 0.001) and
positively associated with post-snack fullness AUC (r: 0.391,
p< 0.003) and time to dinner request (r: 0.535, p< 0.001).
Discussion
The consumption of a 160 kcal afternoon yogurt snacks, varying
in protein content, led to reduced afternoon hunger, increased full-
ness, and delayed the onset of eating. Additional benefits were
shown with the high protein snack containing 24 g of protein.
These data suggest that a small, high protein afternoon snack reg-
imen might delay or prevent subsequent snacking and over-eating
later in the day. Further research to critically test this hypothesis is
warranted.
Snacking is an increasingly common daily habit practiced
among nearly all (i.e., 97%) adult Americans and has closely mir-
rored the rise in obesity (Piernas & Popkin, 2010). Although snack-
ing is often triggered by physiological hunger, many people often
snack due to environmental stimuli such as TV ads, social events,
and snack availability or as a result of emotional and/or psycholog-
ical factors including boredom, reward/fun, and/or stress (Johnson
& Anderson, 2010; Sloan, 2009). Unfortunately, many of the com-
monly consumed snacks readily available are those which are
nutrient-poor yet energy dense foods including desserts, salty
snacks, and sugar-sweetened beverages (Piernas & Popkin, 2010).
To date, almost 30% of daily intake (700 kcal/d) is comprised of
these unhealthy, afternoon/evening snacks (Piernas & Popkin,
2010). It is currently unknown as to whether the frequency, size,
or quality of these snacks has the greatest influence on energy in-
take regulation and/or body weight management. However, cur-
rent trends indicate that Americans have an increased desire to
purchase and consume healthier snack options (Sloan, 2011). Since
yogurt is a good source of calcium and other vitamins and miner-
als, contains probiotics, and is higher in protein than most other
snacks, it is generally considered a healthy, nutritious snack. This
may, in part, explain the increased yogurt sales in the US (Sloan,
2011; Stachura, 2010).
The consumption of high protein foods, meals, and overall diets
have led to improved appetite control, satiety, reduced reward-
driven eating behavior, and reduced daily energy intake compared
to high CHO and/or high fat versions (Batterham, Heffron, et al.,
2006; Holt, Miller, et al., 1995; Leidy, Armstrong, et al., 2010; Leidy,
Lepping, et al., 2011; Leidy & Mattes et al., 2007; Marmonier et al.,
2000; Poppitt, Proctor, et al., 2011; Potier, Fromentin, et al., 2009;
Skov, Toubro, et al., 1999; Weigle, Breen, et al., 2005; Westerterp-
Plantenga et al., 2009). Although many of these studies incorporate
the additional dietary protein in larger meals containing quantities
of P28 g/eating occasion, a few protein-rich snack studies have
been completed.
In 2000, Marmonier et al. (Marmonier et al., 2000) compared
the consumption of 235 kcal afternoon snacks, varying in
macronutrients, on afternoon hunger, satiety, and the time at
which dinner was spontaneously requested. In general, snacking
led to reductions in afternoon hunger and increases in afternoon
fullness (satiety) compared to no snacking (Marmonier et al.,
2000). Although no differences in perceived sensations were ob-
served between snack types, the high protein (46 g protein) snack
led to a delay in the request for dinner compared to the high fat
and/or high CHO snacks (Marmonier et al., 2000).
In a more recent study (Poppitt et al., 2011), water beverages,
varying in protein quantities (i.e., 0–20 g) were consumed 2 h after
breakfast. In this study, perceived appetite and satiety were as-
sessed throughout the day. Additionally, the time during which
hunger and fullness returned to baseline were assessed. Increasing
the protein content in the water beverages led to reductions in
morning hunger and increased morning fullness. Furthermore,
hunger was suppressed and fullness was maintained longer when
the 20 g protein-rich water beverages were consumed compared to
plain water. Lastly, Potier et al. (2009) examined whether two dif-
ferent 200 kcal cheese ‘snacks’ containing 22 g protein would re-
duce subsequent meal (i.e., lunch) and daily energy intake. Both
high protein snacks led to reduced intake at lunch and over-com-
pensation of the snack throughout the remainder of the day. Unlike
many of these studies, we incorporated a commercially available,
commonly-consumed afternoon snack containing a modest
amount of protein (i.e., 24 g). Regardless of the experimental de-
sign differences, we also found reduced hunger, increased satiety,
and delayed onset of eating following the high protein yogurt vs.
no snack or consuming lower-protein yogurts. Additionally, we
also examined whether the 160 kcal afternoon snack would be
fully compensated for at the dinner meal. Similar to the findings
of Marmonier et al. (2000) and Potier et al. (2009), we also only
found partial compensation of the snack energy content at dinner,
with no differences between yogurt snacks. However, Potier et al.
(2009) also examined daily intake and found that the 200 kcal
(22 g protein) morning snack was actually over-compensated for
by the end of the day with compensation of approximately 132%
(i.e., 300 kcal/d less than when no snack is provided). Thus, it is
plausible that the high protein, afternoon yogurt snack provided
in our study might lead to similar compensatory eating behaviors
throughout the evening.
One of the more novel procedures incorporated in the current
study as well as other published studies (Cummings, Frayo, et al.,
2004; Marmonier et al., 2000) involved the use of voluntarily eat-
ing request. The majority of acute studies typically incorporate a
fixed-meal design in which the study participants are required to
eat at a set time, regardless of ‘physiological hunger’ or motiva-
tional drive to eat. Thus, by allowing each participant to choose
when they desire to eat, we are able to assess satiety as well as
motivational drive to eat. One caveat with this approach is making
sure the participants are blinded to all time cues to avoid request-
ing dinner based on environmental stimuli instead of physiological
cues. During the testing days, all windows were covered; watches,
wall-mounted clocks, and laptop clocks were removed; and cell
phones were turned off. In order to assess whether the participants
Fig. 4. Eating initiation as assessed from time to dinner request.

No snack (NS) vs.
All snacks, p< 0.05;

high protein (HP) vs. low protein (LP), p< 0.05;
à
HP vs.
moderate protein (MP), p< 0.05.
S.M. Douglas et al. / Appetite 60 (2013) 117–122 121

were aware of time cues, we asked them what time they thought it
was after they indicated they were ready to request dinner. The ac-
tual time of day and the participant-estimated time of day coin-
cided only 30% of the time. Therefore, it is reasonable to
conclude that the participants were effectively screened from all
time cues.
The main study limitation is the varying dietary and sensory
snack characteristics between the yogurt snacks outside of the dif-
fering quantities of dietary protein. As discussed in Sorensen,
Moller, et al. (2003), increased palatability, sweetness, and flavor
intensity consistently lead to increased food intake; however,
conflicting data exist with respect to their effects on appetite and
satiety. In the current study, we assessed perceptions of aroma,
flavor, texture, appearance, and palatability (like) for each yogurt.
Flavor was the only sensory component that differed between
yogurts. This only occurred between the MP vs. HP yogurt with
the MP yogurt characterized with weaker flavor vs. HP yogurt
(p< 0.05). When included in the mixed factor ANOVA, none of
these factors ended up remaining in the model as covariates.
Although the varying sensory characteristics appear to have mini-
mal effect on study outcomes, it is possible that the varying dietary
factors might have influenced the study findings. These include
dietary non-nutrients, fixed variables such as volume, mass, viscos-
ity, and energy density as well as the dietary nutrients, namely
macronutrient composition.
Foods and/or beverages of greater mass, volume, and/or viscos-
ity or lower energy density generally reduce appetite, increase sati-
ety, and/or reduce subsequent energy intake compared to high
energy-dense foods (see reviews (Rolls, 2009; Welch, 2011)). These
effects can be attributed to the increased amount of water and gas
infused into these foods and/or beverages (Welch, 2011). In our
current study, mass, volume, and energy density were similar be-
tween the low and moderate protein yogurts, whereas the high
protein yogurt exhibited a larger mass and volume but lower en-
ergy density. Because these differences might have substantially
contributed to the differences in perceived hunger, satiety, and
the onset of eating, caution is warranted when interpreting the
findings solely based on protein quantity of the afternoon snacks.
It is important to note, however, that a myriad of studies exist
examining the effects of high protein meals and/or diets and col-
lectively show reduce appetite, increase satiety, reduced onset of
eating, and reduce subsequent intake compared to low protein ver-
sions (Halton & Hu, 2004; Veldhorst et al., 2008; Westerterp-Plant-
enga et al., 2009). Although some argue that the effects shown with
increased dietary protein are primarily a result of the reduction in
carbohydrates and not the increase in protein, similar findings oc-
cur with high protein diets when carbohydrates are maintained
and dietary fat is reduced (Weigle et al., 2005).
In an attempt to assess the impact of the previously discussed
snack characteristics on the main study outcome, that being time
to dinner request, a multivariate, backward regression was per-
formed. Protein content and palatability of the snacks were the
only factors that significantly predicted the onset of eating,
accounting for 46.2% of the variability (p< 0.001).
In summary, we found that a 160 kcal afternoon Greek yogurt
snack, containing 24 g of protein, led to reduced afternoon appe-
tite, increased satiety, and delayed the onset of eating in healthy
women. These findings suggest that the daily incorporation of high
protein, afternoon snacks may prevent further snacking and poten-
tially overeating throughout the afternoon and evening hours.
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